Microvesicle Analysis Interest Development Group

Mission and Objectives

Welcome to the ISAC Microvesicle Analysis Interest Group web page. Our goal is to provide a forum for information and interaction to enable and standardize the quantitative and multiparameter analysis of small cell-derived membrane vesicles.

Cell-derived Membrane Vesicles

Mammalian cells release small membrane vesicles that can carry biological molecules and signals to exert biological effects at a distance. Exosomes are membrane vesicles of intracellular origin that are secreted from the cell by exocytosis. Ectosomes, also commonly referred to as microvesicles or microparticles, are shed from the plasma membrane. These membrane vesicles have been implicated in a wide range of physiological functions, but their very small size makes them a challenge to analyze.

Flow Cytometry of Microvesicles

Several different measurement approaches can be taken for the analysis of cell-derived microvesicles, and each has their advantages and disadvantages. For example, ELISA-type immunoassays can measure the total amount of a microvesicle-associated antigen in a sample, but do not provide single vesicle information. Optical measurements such as nanoparticle tracking analysis can provide information on the size and number of microvesicles, but not information about the amount of an antigen on individual vesicles. Flow cytometry is distinguished by its ability to measure multiple targets on individual particles, but the small size and dim signals from most microvesicles challenges the sensitivity limits of flow cytometry.

Standardization Efforts

Because of the potential importance of microvesicles as diagnostic or prognostic markers, there is significant interest in standardizing sample preparation and measurement approaches for cell-derived microvesicles. Notable efforts have taken place under the auspices of the International Society for Thrombosis and Hemostasis (ISTH), which has sponsored efforts to attempt to standardize flow cytometry measurements of microvesicles, as well as sample collection and processing steps. These continuing efforts have raised several important issues that impact the analysis of cell derived membrane vesicles, including:

How do differences in light scatter measurement among different commercial flow cytometers affect the microvesicle measurement?

What are the limits of antigen detection on microvesicles using fluorescence-labeled antibodies?

What is the appropriate use of microspheres in standardizing and calibrating instrument for use in measure small microvesicles?

What are the most appropriate gating strategies for analysis of microvesicles?

What is the minimum information that should be reported for a flow cytometry measurement of microvesicles?

Improving the Measurement of Microvesicles

The efforts described above have led to several important insights that will help standardize microvesicle measurements using the current generation of commercial flow cytometers. However, they also highlight the need for new, more sensitive methods for measuring cell-derived vesicles. Toward this end, it is important to address a further set of issues:

What are the best controls or reference samples for standardizing the measurement of microvesicles by any method?

What are the appropriate validation experiments that can define the performance of any new or existing microvesicle analysis method?

Get Involved

If you are interested the analysis of cell-derived membrane vesicles or other nanoparticles, and would like to participate in efforts to standardize and validate both existing measurement approaches and new technologies, you are welcome to join by sending your contact information and a brief description of your interests and expertise to microvesicles@isac-net.org.